Method of making a foamed container having an integral neck portion

ABSTRACT

A METHOD FOR PRODUCING A FOAMED PLASTIC CONTAINER HAVING A BODY PORTION AND A NECK PORTION WHICH ARE INTEGRALLY FORMED. THE BODY PORTION IS ESSENTIALLY CELLULAR AND THE NECK PORTION IS ESSENTIALLY NONCELLULAR. THE BODY PORTION HAS A DENSE SKIN ON ITS SURFACE. THE CONTAINER IS BLOW MOLDED FROM AN INJECTION MOLDED PARISON.

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- METHOD OF MAKING A FUAMLLD CONTAINER HAVING AN INTEGRAL NECK PORTIONFiled July 22, 1964 10 Sheets-Sheet 10 47 we u: Y5

United States Patent 3,558,751 METHOD OF MAKING A FOAMED CONTAINERHAVING AN INTEGRAL NECK PORTION Thomas R. Santelli, Sylvania, Ohio,assignor to Owens- Illinois, Inc., a corporation of OhioContinuation-impart of application Ser. No. 847,144, Oct. 19, 1959. Thisapplication July 22, 1964, Ser. No. 389,511

Int. Cl. B2911 27/00 US. Cl. 264-45 4 Claims ABSTRACT OF THE DISCLOSUREA method for producing a foamed plastic container having a body portionand a neck portion which are integrally formed. The body portion isessentially cellular and the neck portion is essentially noncellular.The body portion has a dense skin on its surface. The container is blowmolded from an injection molded parison.

This application is a continuation-in-part of Ser. No. 847,144, filedOct. 19, 1959, and new Pat. No. 3,144,493.

This invention relates to a method for forming plastic articles havingan end portion in substantially unexpanded or unfoamed condition withthe balance of the article being integral therewith and in expanded orfoamed condition.

Various articles made of foamed or cellular plastics are desirablebecause of the various unique properties of foamed plastics, such ascushioning and insulating effects or because of the savings in materialwhich can be realized when producing the article from a plastic incellular form. However, it has not been desirable to form many objectsfrom cellular plastics in the past because some objects require greaterstrength or rigidity in certain areas or portions than can be offered bythe particular cellular plastic in question.

Typical of such articles or objects which have not been formed on acommercial basis of foamed or cellular plastics are containers of thetype having a finish or neck portion for receiving a closure cap or lid.Since the closures are normally applied by automatic filling and closingequipment the finish must be accurately formed and, further, the finishmust be nonporous and have a densified exterior surface and lip toreceive the closure, while the interior surface of the finish must alsobe nonporous and smooth for accurate filling and for nondrip dispensingof the container contents.

If an attempt were made to form the finish portion of a container in aconventional free extrusion machine, i.e., from an extruded tube orsheet of foamed or cellular plastic material, a dense, smoothly surfacedfinish could be formed only by crushing or otherwise disrupting thealready foamed, cellular structure by compression molding. Such crushingof the cellular structure would destroy the preformed tube and result inan inadequate finish, both from the standpoint of structural strengthand from the standpoint of its structural integrity with the remainderof the container structure. If the entire container, including thefinish, were uniformly foamed or cellular, a finish of lesser strength,of inaccurate contour, and of roughened, nonsealable exterior surfaceswould be provided, and a commercially unacceptable product would againresult.

The present invention now proposes the provision of a plastic containerhaving a body portion and a neck portion which are integrally formed,the body portion being essentially cellular and the neck portion beingessentially noncellular and substantially more dense than the bodyportion, the neck or finish portion having dense, glazed ice interiorand exterior surfaces confining therebetween any cellular material whichmay occur in the neck portion.

Such a container is provided by the method of the present inventionwhich utilizes material which is plasticized while containing anintimately dispersed foaming agent capable of liberating a gas in theplasticized material when the material is subjected to a plasticizingtemperature and a relatively low pressure, i.e., less than the vaporpressure of the gas liberated in the material by the foaming agent. Themethod contemplates the injection molding of at least the finish portionof the container at a superatmospheric pressure which is greater thanthe vapor pressure of the gas liberated in the material by the blowingagent, so that foaming is inhibited in the finish portion and any otherportions of the container which are formed by injection molding.

Subsequently, the injection molding pressure is released after at leastthe finish portion has been injection molded and a blowable bubble isformed from the plasticized material, this blowable bubble beingenclosed within a blow mold and inflated to form the bubble to the finalconfiguration of the body portion of the container.

During the formation of the blowable bubble or during the enclosing ofthe blowable bubble in the blow mold or during the blow moldingoperation, foaming of the plas ticized material is accommodated, so thatthe final blown body portion of the container is cellular and possessesall of the heretofore recited advantages, such as the cushioning andinsulating capabilities of the cellular structure, the substantialsavings of material vbecause of the lower density of the cellularstructure, and the like.

Of course, after the release of the injection molding pressure, somefoaming may occur, even within the finish portion of the container orother article, since the material which has been injection molded stillcontains the blowing agent which may effect cellulation in the still-hotinner portions of the injected finish under the lessened pressure.However, any foaming or cellular structure which may result will beconfined between heavy, densified surface layers formed by contact ofthe material with the chill surfaces of the injection mold, and all ofthe surfaces contacting the injection mold will be finally stabilizedprior to the release of the injection molding pressures. Thus, thefinish will possess all of the advantages heretofore recited of contouraccuracy, surface smoothness, structural rigidity and the like, eventhough some small amount of foaming may occur within the finish portion.

It is, therefore, an object of the invention to provide a method forproducing a cellular plastic article having an end portion which is in asubstantially unexpanded condition and integral with the cellularportion of the plastic article.

An additional object of the present invention is the provision of amethod of making a container or the like having an injection moldedfinish portion and a blow molded body portion, the article being formedof a material having incorporated therein a blowing agent, by thesequential injection molding of the finish portion under conditionsinhibiting foaming of the plasticized material, followed by theformation of a blowable bubble which is subsequently blown to shape, theforming and blowing being accomplished under conditions whichaccommodate foaming of the body portion to a cellular structure integralwith the finish portion, and confining any cellular structure whichmight occur in the neck portion, or in the finish portion betweendensified, stable, noncellular surfaces.

Yet another and no less important object of the present invention is theprovision of a blow molded article such as a container having a finishportion integral with a blown body portion, the finish portion havingdense, glazed interior and exterior surfaces between which is 3 confinedany cellular material occurring in the finish portion while the bodyportion of the article is essentially cellular in nature.

Other objects and advantages of the invention will become apparent froma consideration of the accompanying disclosure and the drawings.

According to the invention, there is provided a method which comprisesproviding a quantity of hot plasticized plastic material containing anintimately dispersed foaming or cellulating agent, forming asubstantially unexpanded, essentially noncellular shaped end portion ofan article from a portion of said plastic material under shapingconditions which prevent any substantial foaming of said portion of saidfoaming agent, from another portion of said quantity of plastic materialforming the balance of said article integral with said shaped endportion under conditions whereby said second portion of said article isexpanded into a cellular structure by the action of said foaming agent.

Further, according to the invention there is produced a plastic articlehaving a cellular portion integral with an end portion formed from thesame plastic composition as said cellular portion, said end portionbeing in a substantially solid or unexpanded, noncellular condition.

Blowing or foaming agents which are dispersed in plastics are of twomain general types. In the first type the blowing agent is a chemicalblowing agent, that is, one which evolves a gas under the influence ofheat by chemical reaction or chemical decomposition. The second type ofblowing agent is a physical blowing agent, such as a volatile liquiddispersed in the plastic, such liquid forming a gas or vapor under theinfluence of elevated temperatures and/ or lowered pressures. Suchfoaming agents are well known and will not be discussed in detail here.Either type of blowing agent is applicable in the present invention,since either type is capable of liberating a gas in the material so longas the vapor pressure of the gas so liberated is greater than theexternal pressure exerted on the material.

Chemical foaming agents are usually employed at a concentration of fromabout 0.5 to weight percent of the plastic composition, including thefoaming agent, although higher or lower amounts are applicable.

The nature of the invention will be better understood from a descriptionof the drawings which illustrate several suitable types of apparatus forcarrying out the method and producing the article of the invention.

Referring to the accompanying drawings:

FIGS. 1 through 6, inclusive, are sectional elevational views of onesuitable apparatus for performing the method, showing the parts indifferent positions corresponding to various steps of the method;

FIGS. 7 through 10, and 13, 14 and 15, inclusive, are sectionalelevational views of another apparatus for performing the method,showing the parts in different positions corresponding to the varioussteps in the method;

FIG. 11 is a sectional view at the line 1111 of FIG. 9;

FIG. 12 is a sectional view at the line 12-12 of FIG. 7;

FIGS. 16, 17 and 18 illustrate sectional views of another apparatussiutable for effecting the method of the invention, showing the parts indifferent positions.

FIGS. 19 through 22, inclusive, are sectional elevational views of amodified form of apparatus, capable of performing the method, theseviews illustrating successive steps of the method;

FIG. 23 is a fragmentary vertical sectional view of a container of thepresent invention manufactured by carrying out the steps of the processillustrated in FIGS. 19 through 22;

FIGS. 24, and 26 are vertical sectional views illustrating still anotherform of apparatus capable of carrying out a modified form of the methodof the present invention, these views illustrating successive steps ofthe method; and

FIG. 27 is a view illustrating an article of the present inventionmanufactured by the method as illustrated in FIGS. 24 through 26.

THE EMBODIMENT OF FIGS. 1 THROUGH 6 As shown in FIGS. 1 through 6, anapparatus for performing the method includes a body 20 having a verticalopening therethrough and an orifice ring 21 overlying the verticalopening. A mandrel 22 is positioned in the opening thereby forming atubular cavity 23. The tubular cavity 23 is in communication with theoutlet of a plasticizer and extruder (not shown) through a channel 24.

A sleeve 25 surrounds the mandrel 22 and is reciprocable by means (notshown) from a position above and overlying the channel 24 to a lowerposition whereby the tubular cavity 23 can be brought into and out ofcommunication with the channel 24.

A partible neck mold 26 and a hollow core 27 are mounted above the body20 for axial movement into and out of alignment with the open end of thecavity 23. A partible finishing mold 28 (FIGS. 5 and 6) is provided forexpanding the plastic tube to finished form, as hereinafter described.The bottom of the mold sections are beveled at 29 and spaced apart at 30in order to pinch the plastic material and seal the end thereof.

At the beginning of the operation of the apparatus shown in FIGS. 1through 6, a quantity of hot plasticized material containing foamingagent material, and sufficient to fill the tubular cavity, is introducedfrom the source of plastic through the channel 24 to the cavity. Themass of plastic material in the tubular cavity is isolated from theparent mass of plastic material by movement of the sleeve 25 upwardlyacross the channel 24. The apparatus is then in position for thebeginning of the cycle and the neck mold 26 is brought into contact withthe body 20, the core 27 contacting the mandrel 22 (FIG. 1).

The sleeve 25 is then moved upwardly under controlled pressure asufficient distance to force a portion of the plastic material in thetubular cavity upwardly in order to fill the neck mold 26 and form thefinish or end portion of the article (FIG. 2). The sleeve 25 is thenretracted downwardly to reestablish communication with the plasticmaterial (FIG. 3). Simultaneously, the neck mold is moved upwardly andaxially away from the end of the cavity. The pressure of plasticmaterial from the parent mass forces plastic material into the tubularcavity, and prevents any substantial expansion by foaming of the plasticin the neck mold. Also, the mold chills the plastic sufficiently thatexpansion is avoided when the neck mold is later removed. A portion ofthe plastic material in the cavity 23 is displaced out of the open endof the cavity, thereby forming a length of tubing integral with theneck. As this tubing is formed, the foaming agent therein causesexpansion into a tube of foamed or cellular plastic as it issues fromthe cavity. As the desired length of tubing is formed, the sleeve isagain moved upwardly to cut off or resegregate the parent mass from theplastic material in the tubular cavity. A shear blade 31 is then movedacross the orifice to sever the length of tubing from the plasticmaterial in the tubular cavity (FIG. 4).

The sections of the hollow mold 28 may then be closed about the plasticmaterial, thereby pinching the lower end of the tubing. The foamedtubing can then be expanded to the confines of the mold by applyingfluid under pressure through the hollow core 27 (FIGS. 5 and 6).

After the tubing has been severed from the plastic material in thecavity (FIG. 4), the apparatus is again in position for beginning thecycle by bringing a neck mold into contact with the body 20 and formingthe neck finish by moving the sleeve 25 upwardly.

A modification of the method can be performed by retracting the sleeve25 at the beginning of the cycle as shown in FIG. a to permit a limitedquantity of plastic to enter the tubular cavity and then moving thesleeve upwardly, simultaneously isolating the quantity of plastic in thetubular cavity and forcing plastic into the neck mold positioned overthe cavity, as shown by FIGS. 2 and 8. The sleeve is then retracted andthe neck mold moved axially away from the cavity to form a length oftubing integral with the neck, in the same manner as heretoforedescribed. As the desired length of tubing is formed, the sleeve isagain moved upwardly, as in FIG. 4, or rotated as in FIG- 10, to isolateor resegregate the plastic material in the cavity and the length oftubing is severed. The cycle of operations can then again be started bythe retraction of the sleeve.

THE EMBODIMENT OF FIGS. 7 THROUGH 15 Another apparatus for performingthe method is shown in FIGS. 7 through 15, inclusive. In this apparatusthe sleeve 25' is provided with a slot or groove 32 extendinglongitudinally along the outer surface of the sleeve to the upper endthereof. In the operation of this apparatus, the tubular cavity isinitially filled with plastic material containing foaming agent, as inthe form of the apparatus shown in FIGS. 1 through 6. The sleeve 25' isin the position shown in FIG. 7 wherein the plastic material in thetubular cavity is isolated or segregated from communication with theparent mass and the groove 32 is in a position out of communication withthe channel 24 (FIG. 12). The sleeve 25' is then moved upwardly to forceplastic material into the neck mold, thereby forming the neck finish(FIG. 8). The sleeve is then rotated to bring the groove 32 intocommunication with the channel 24, thereby permitting plastic materialto flow from the parent mass to the tubular cavity (FIGS. 9, l1).Simultaneously with this action, the neck mold is moved axially awayfrom the cavity, thereby forming a length of tubing integral with theneck finish by the flow of plastic material out of the tubular cavity.During the forming of the tubing the sleeve is retracted into its lowerposition. As the desired length of tubing is formed, the sleeve is againrotated to bring the groove 32 out of register with the channel 24isolating or resegregating the plastic material in the cavity from theparent mass (FIG. 10).

The neck finish and integral tubing can then be severed (FIG. 10) andsealed and expanded, as shown in FIGS. 13 and 14, by closing the moldsections and supplying fluid under pressure through the core.

At the severing of the tube from the material in the tubular cavity, thevarious parts are again in position for application of pressure to themass of plastic in the tubular cavity to force plastic out of thetubular cavity and once again begin the cycle of forming a hollowplastic container.

THE EMBODIMENT OF FIGS. 16, 17 AND 18 In FIGS. 16, 17 and 18 there isillustrated another method for making a somewhat different articleaccording to the invention. This specific article illustrated is asolid, substantially unfoamed bottle cap having a central plug portionin foamed condition. The illustrated apparatus includes a body 34 havinga vertical opening therethrough and an orifice 35 overlying the verticalopening. The vertical opening 36 is in communication with the outlet ofa plasticizer and extruder (not shown) through a channel 37. A plunger38 is positioned in opening 36 and is reciprocable by means (not shown)from a position well above opening 35, such as the position shown inFIG. 17 to a lower position, such as shown in FIG. 16, whereby theopening 36 can be brought in and out of communication with orifice 35.

A partible mold 33 is mounted above the body 34 for axial movement intoand out of alignment with the orifice 35.

At the beginning of the operation of the apparatus shown in FIGS. 16through 18, the respective parts of the apparatus are as shown in FIG.18, except that the mold 33 contains no plastic. A quantity of plasticcontaining foaming agent has already been introduced into opening 36through the channel 37 as shown in FIG. 18. The mold is moved intoalignment with orifice 35 so as to close the apparatus and the plunger38 is reciprocated downwardly to a position shown in FIG. 16, allowing ameasured quantity of hot plasticized material to move into the opening,as shown in FIG. 16. The plunger is moved to a position shown in FIG.17, thus ramming the plastic into the mold. The plunger 38 is held inthat position for a short period. Then mold 33 is again moved upwardlyto the position shown in FIG. 18, allowing the central portion of theplastic containing a foaming agent to expand downwardly through thechannel of the mold to form a foamed core. The plunger 38 is moved tothe position shown in FIG. 18, ready for the next cycle. After themolded part has sufficiently hardened, the mold 33 is parted and themolded article removed therefrom.

In the foregoing operation the relatively thin sections of the bottlecap illustrated as being made of solid plastic are cooled sufficientlyby the mold 33, while under the pressure of the ram in the positionshown in FIG. 17, that the plastic is hardened and the foaming agent inthat portion of the plastic is not effective to cause any substantialexpansion of the plastic, thus causing this portion of the molded pieceto be in a solid, substantially unfoamed, unexpanded condition. Indirectcooling means can be provided in the mold around this portion of themolded article, if desired, to assist in the cooling. The centralportion of the plastic in the mold, as shown in FIG. 17, does not becomesufficiently cooled during the injection molding step to set up orharden, and when the mold is separated from the plunger and the opening35, the still-hot, plasticized plastic containing foaming agent foamsunder the influence of the foaming agent, thus forming the cellular plugstructure illustrated.

An advantage of the process of the invention is that there is not asharp line of demarcation between the fully foamed body and thesubstantially unexpanded, solid end portion of the article producedaccording to the process. Thus, there is a gradual decrease in the bulkdensity from the solid end portion to the fully foamed main portion ofthe fully foamed body. Thus, the articles of the in vention might besaid to have three zones: a substantially unexpanded end portion, andintegral and continuous with said end portion, a cellular portion of thesame plastic composition as said end portion; a zone of the cellularportion adjacent the unexpanded end portion having a higher bulk densitythan the bulk of the cellular portion of the article. The gradualdecrease in density in this intermediate zone gives a superior productin that the strength on flexing is increased because there is no sharpline of demarcation between the solid and the fully foamed portions.

The following examples illustrate the methods and articles made fromvarious thermoplastics, but the examples are illustrative only and arenot to be taken as limiting the invention.

EXAMPLE I Low density polyethylene in particle form containingp,p-oxybis (benzenesulfonyl hydrazide) as a foaming agent was introducedinto a molding machine of the type of FIGS. 1 to 6, where it was heatedand plasticized to a workable condition. This foaming agent has adecomposition range of about to C. Bottles were molded using the machineas described in the description of FIGS. 1 through 6. The temperature inchannel 24 and tubular cavity 23 was maintained at about 305 F. Thepressure during the step shown in FIG. 2 was theoretically about 1800p.s.i.g., although actual pressure may have been somewhat less due tofriction losses. A bottle was molded in the manner described withrespect to FIGS. 1 through 6, and the resulting bottle had a cellularfoamed structure while the neck or finish was substantially solid andunexpanded.

In the cycle of operations the time of the total cycle was 31 seconds,while the time from the beginning of the cycle shown in FIG. 1 to thetime the sleeve 25 reached the position shown in FIG. 3 was 2.6 seconds.Sixty bottles were molded in this manner.

EXAMPLE II The procedure described in Example I was repeated, but usinga high density linear polyethylene having a den-' sity of about 0.96gm./cm. and a melting point of about 260 F. This polyethylene contained1.0 percent by weight 1,1-azobis(formamide) as the foaming agent. Thetemperature in the channel 24 and the cavity 23 was maintained at about315 F. The bottle again had a substantially solid unexpanded neck orfinish portion integral with a cellular body portion.

EXAMPLE III The procedure of Example I was again repeated but usingparticulate polystyrene containing pentane intimately dispersed thereinas a foaming agent.

The temperature in the channel 24 and the cavity 23 was maintained atabout 325 F.

The bottle so produced had a substantially solid, unexpanded neck orfinish integral with a foamed body portion of very fine-celled foamedstructure.

In the embodiment of the method described with respect to FIGS. 1through 6, and with respect to FIGS. 7 through 15, the step of blowingwith air as in FIGS. 5 and 6 and FIGS. 13 and 14 can be omitted wherethe dimensions of the foamed body of the article are not desired to begreater than produced by the step shown in FIG. 4 or FIG. 10. Thetubular foamed extruded body is merely cooled in place, and can bepinched together at the end, and severed, and removed from the apparatusas a finished article.

The invention has been described as being applied to organic plasticmaterials. The terms plastic and thermoplastic, as used herein, defineany organic material which has the required condition of plasticity topermit expansion and setting in predetermined form.

The terms tubular and tubing, as used herein, are intended to includeany hollow shapes in which plastic material can be formed, includingnoncircular and irregular shapes.

THE EMBODIMENT OF FIGURES 19 THROUGH 23 In the earlier describedembodiments of the present invention, only the neck or finish portion ofthe container has been injection molded in order to yield the dense,smooth, substantially noncellular surface portions which are necessaryto the manufacture of a commercially acceptable container. In theembodiment of FIGS. 19 through 23, this concept of injection molding andthe formation of smooth, substantially noncellular, dense surfaceportions is carried even further to yield a container body portionhaving extremely desirable characteristics, particularly well adapted tothe container art.

More specifically, in FIG. 19, a plasticiZer-extruder indicatedgenerally at 50, comprises a generally cylindrical barrel 51 havingdisposed therein a plasticizer-extruder screw 52 provided with a raisedhelical peripheral thread 53. The screw 52 and the thread 53 areschematically illustrated and are capable of plasticizing pelletizedplastic material, such as polyethylene, polystyrene or the like,containing a bowing agent capable of liberating a celluating or foaminggas when subjected to elevated temperatures and relatively lowpressures, as heretofore explained.

Such material is supplied to the barrel 51 through a barrel inletaperture 54 communicating with an upper, gravity-feed hopper 55. Thescrew 52 is disposed interiorly of the bore 56 of the barrel 51 for bothrotational movement and axial displacement. The screw 52 is retated bymeans of a drive shaft 57 coaxial with the screw and projecting throughan aperture 58 formed in the rear wall of the barrel 51 to carry a spurgear 59 engaging a driving gear 60 driven by suitable means, as by anelectric motor 61. The screw is actuated axially by means of anactuating cylinder 62 having disposed therein a piston 63 secured to theshaft 57. The cylinder 62 is fluid pressure actuated by pressurizedfluid introduced thereinto through supply lines 64 communicating withthe suitable source of such fluid.

The barrel bore 56 communicates at its forward open end 65 with a supplyblock 66 having a vertical bore 67 therethrough and a transverse passage68 communicating with the barrel bore end 65. Vertically reciprocablewithin the bore 67 of the block 66 is an injection ram 69 actuated by afluid pressure actuated cylinder 69a.

Disposed over the vertical bore 67 is a parison mold indicated generallyat 70 and comprising laterally separable parison mold halves 71cooperatively defining therebetween a parison mold space 72 normallyopen at its lower end for full communication with the vertical bore 67of the block 66.

Superimposed over the parison mold 70 is a neck ring mold indicatedgenerally at 73 and comprising a pair of neck mold halves 74 havinginwardly projecting flanges 75 cooperably defining therebetween a neckmold space 76 in full communication with the parison mold space 72.Surrounded by the neck mold halves 74 is an upper collar 77 abutting alower neck mold sleeve 78 having an inner peripheral flange 79projecting internally of the flanges 75 of the neck mold halves 74 anddownwardly into the mold space 72 to cooperatively define the mold space76 with the flanges 75, i.e., the interior ring flange 79 defines theinner surface of the mold space 76 while the neck mold flanges 75 definethe exterior surfaces thereof.

Projecting vertically downwardly through the ring 77 and depending intothe mold space 72 is an internal parison sleeve indicated generally at80 and comprising an upper cylindrical wall portion 81 projectingaxially through the flanges 79 and a lower tapered portion 82 definingthe interior surface of the mold space 72 and terminating in a lowerperipheral edge 83 in spaced relation to the supply block 66. Projectingaxially of the parison sleeve 80 is a valve actuating rod 84 terminatingin a radially enlarged valve head 85 normally abutting the terminal edge83 of the sleeve portion 82, this head 85 thus being interposed betweenthe sleeve 82 and the supply block 66.

The overall apparatus illustrated in FIG. 19 of the drawings isdisclosed in greater detail in my application Ser. No. 146,686, nowabandoned, while the reciprocating screw plasticizer-extruder 50 is ofthe type disclosed in greater detail in the copending application ofHans G. Stenger, Ser. No. 185,757, filed Apr. 6, 1962, and assigned tothe assignee of the present invention, and now Pat. No. 3,188,691.

In operation, the motor 61 is actuated to rotationally drive the screw52, while the ram 69 is actuated by the cylinder 69a across the aperture68 to isolate the bore 67 from the barrel outlet opening 65. Rotation ofthe screw 52 will displace to the right the particulate plastic materialcontaining the foaming agent entering the barrel bore 56 through theaperture 54 from the hopper 55. The design of the screw 52 is such thatthis material becomes plasticized and is maintained under heat andpressure conditions such that the foaming agent is ineffective to causefoaming of the material while the material is confined within the bore56. This plasticized material will be accumulated under pressure betweenthe righthand outlet end of the screw 52 and the ram 69, theaccumulation of the material forcing the screw 52 backwardly against theback pressure of the cylinder 62 in the manner described in connectionwith the above identified Stenger application.

After such a body of plasticized material under pressure has beenaccumulated, the ram 69 need merely be actuated downwardly by thecylinder 69a as the screw 52 is advanced to the right by the cylinder62, thereby depositing in the bore 69 a charge of material which isplasticized and still in a nonfoamed condition. The ram 69 is nowactuated upwardly by means of the cylinder 6% to deposit this charge ofmaterial in theparison mold space 72 and in the neck mold space 76.Thus, the ram 69 acts as the pressure generating element for aninjection mold, this mold being defined by the parison mold sections 71,the internal sleeve 80, the internal neck flange 79 and the externalneck ring flanges 75 and by the ram 69 which closes the open bottom ofthe mold space 72. The plasticized material will be injected into, andinjection molded 'within, the mold spaces 72, 76 in such manner as toform a completely injection molded parison, indicated generally at 90 inFIG. 19.

Preferably, the neck mold flanges 75 and the internal flanges 79 arechilled by an external chilling means while the material filling theparison mold space 72 is not chilled to the same extent. However, thematerial in both the mold chambers 72, 76 is maintained under injectionpressure which is greater than the vapor pressure which can be generatedinternally of the plasticized material by the gas liberated therein bythe foaming agent. Thus, substantially no foaming occurs during theinjection molding portion of the cycle illustrated in FIG. 19.

Of course, there is necessarily going to be some chilling of thematerial in the parison mold 70 but substantially less chilling effectwill be obtained, due to the differential chilling exerted by thecirculation of water for cooling and warming through the passagesdescribed in my above identified application. As a result, thoseportions of the plasticized material in the upper chamber 76 will besubstantially completely solidified as above explained in connectionwith earlier embodiments of the invention, while only interior andexterior surface skins of relatively minute thickness, substantiallyless than the overall thickness of the plasticized material confined inthe parison mold 72, will be formed in the parison mold.

Next, the injection molded parison is stripped from the parison moldwhile retaining those elements defining the neck mold chamber 76 inposition. This operation is illustrated in FIG. 20 of the drawings, andthis operation preferably is carried out by vertically upwardlydisplacing th neck mold section 72, the sleeve 77, the ring flange 79,the sleeve 80 and the associated valving parts 84, 85.

During or immediately after this upward stripping motion which may, ifdesired, be aided by lateral relative separation of the parison moldsections 71, the valve stem 84 is preferably actuated downwardly, asillustrated in FIGS. 20 and 21, and a relatively minute quantity ofblow-air under a low pressure is introduced through the sleeve 80 intothe parison 90. The parison is thus somewhat inflated or puffed to movethe parison radially outwardly away from the internal sleeve portion 82,this sleeve portion being moved vertically upwardly to expose theinternal surfaces of the parison to the blow air.

Once the parison is stripped from the parison mold sections 71, theparison is subjected to atmospheric pressure conditions and, since theparison is still warm, the foaming agent incorporated in the plasticizedmaterial can now liberate the foaming or cellulating gas to foam theplasticized material. However, due to the relative, controlled chillingof the internal and external surfaces of the lower portion of theparison during the injection molding, a chilled skin is formed thereonboth internally and externally of this portion of the parison, and anysubsequent foaming will be confined between these skins. As a result,foaming will occur as may be readily ascertained by a comparison of theparison, as illustrated in FIGS. 19, 20 and 21.

Finally, the puffed or partially inflated parison of FIG. 21 istransferred to a blow molding station at which the lower portions of theparison are enclosed in a pair of separable blow mold sections,indicated at 91, these blow mold sections cooperatively defining aninternal cavity 92 conforming to the configuration of the final blownbody portion of the container. After the parison has been so enclosed,blow air at a relatively high pressure, i.e., on the order of 100 poundsper square inch, is introduced into the parison and the parison isinflated against the walls of the blow mold sections to its finalconfiguration. As illustrated in the greatly enlarged cross-sectionalview of FIG. 23, the neck or finish 93- of the final container 95 isintegral with the body portion of the container indicated generally at94.

Referring now to the body portion 94 of the container, it will be notedthat this portion consists of an exterior or outer skin 96 and aninterior or inner skin 97 having interposed therebetween foamed cellularmaterial 98. As above described, the exterior skin 96 results fromcontact between the injection molded material filling the parison moldand contacting the parison mold sections, while the inner surface 97 isthe result of contact between the plasticized, initially nonfoamedmaterial and the parison sleeve. The foamed inner portion 98 is formedby the foaming which occurs during formation of the blowable bubbleillustrated in FIGS. 20 and 21, this formation of a bubble occurringafter the injection molding pressure has been released. Thus, the skins96, 97 at the exterior and interior surfaces of the container are formedduring the injection molding cycle While the intermediate foamed portion98 is subsequently formed after the pressure of injection molding hasbeen relieved and the conditions are such that the internal pressuresgenerated by the foaming agent, i.e., the vapor pressure of the gasesevolved by the foaming agent, exceed the external pressure upon theparison.

Referring now to the injection molded finish 93, it will be seen thatthis finish is substantially noncellular due to the fact that the neckmold space is retained closed during the complete forming cycle, eventhough the injection molding pressure is relieved immediately prior tostripping of the subsequently blown parison portions from the parisonmold halves. Further, the neck mold is chilled by external chillingmeans to an extent substantially greater than the chilling effect whichis exerted upon the remainder of the parison, so that substantially allof the finish is chilled to a temperature such that foaming does notoccur even though the pressure is relieved. However, the innermostportions of the finish may be at a temperature such that some foamingcan occur following the relieving of the injection molding pressure, andit may well be that isolated pockets of foamed material will occur inthe finish, such pockets being indicated by reference numeral 99.However, the finish is still substantially noncellular and whateverfoaming may occur must necessarily occur only internally of the finishand between the smooth, dense, noncellular surface portions of thefinish, indicated by reference numerals 100 and 101, respectively.

Further, it will be noted that there is a transition zone of cellularmaterial indicated by reference numeral 102 interposed between thefinish 93 and the body 94 of the article, as heretofore described.

Finally, the body 94 of the article is of enhanced structural strengthbecause of the sandwich structure provided by the external, dense,smooth layers 96, 97 having the foamed or cellular structure 98interposed therebetween. Additionally, the body portion is lesspermeable to fluids, either gaseous or liquid, by virtue of surfacelayers 96, 97, thereby enhancing the commercial acceptability of thecontainer for liquid storage and dispensing.

THE EMBODIMENT OF FIGS. 24 THROUGH 27 In that form of the inventionillustrated in FIGS. 24 through 27, inclusive, there is disclosedanother method for making a container. In this instance, the containeris of a slightly different type in that it has an enlarged peripheralopening which can properly be termed a finish. Since this finish isadapted to receive a closure, such as a cap, telescopically fitted overthe finish and engaging either the inner or the outer periphery thereof,the same problems exist as heretofore discussed in connection with theearlier embodiments of the present invention, if this finish werecompletely cellular.

As illustrated in FIG. 24 of the invention, plasticized material issupplied through a supply channel or bore 111 formed in an ejectionnozzle 112 to a mold space 113 defined between an upper injection moldelement 114 and a lower injection mold e ement 115. The upper surface116 of the lower injection mold element 115 is preferably planar inconfiguration and is provided with a central opening 117 through whichthe plasticized material is supplied from the channel 111. Theundersurface of the upper mold element 114 is recessed to provide asubstantially planar blank having an outer peripheral edge 118, anupwardly projecting concave recess 119 adjacent the annular edge, and adownwardly and inwardly, slightly convex surface 120. The upper moldelement 114 is provided with a central cylindrical recess 121communicating with an upper, generally cylindrical bore 122 receivingtherein a vertically displaceable blowing plug, indicated generally at123. This plug 123 has an enlarged head 124 seated in the recess 121with the undersurface 125 of the head defining the central portion ofthe mold space 113. The head is integrally formed with a vertica lyupwardly projecting actuating stem 126 having a central, axial recess127 communicating with a pair of transverse fluid ports \128 for apurpose to be hereinafter more fully described.

From an inspection of FIGS. 24 and 25 it will be seen that the injectionof plasticized material into the mold space 113 results in the formationof a substantially ciroular disc-like blank 130 having its outerperiphery provided with an upwardly enlarged terminal embossment 131 andhaving a flat, inwardly tapering central portion 132 joining theenlarged rim 131 to a central circular portion 133 of substantiallyreduced thickness directly underlying the enlarged head 124.Additionally, it will be noticed that the upper mold element 114 isprovided with a pair of coolant passages 135 positioned immediatelyadjacent the annular rim or flange 131 of the blank and serving to aidin extracting heat from the peripheral edge 131 of the blank during theinjection molding portion of the cycle illustrated in FIG. 24.

Following the formation of the substantially planar blank 130, the blankis stripped from the injection mold 110 by relative displacement of themold elements 114, 115, the blank adhering to the upper mold section 114as the mold section is positioned over a blow mold, indicated generallyby reference numeral 140 in FIG. 25. This blow mold 140 has an internalrecess 141 conforming to the final desired configuration of the articleto be formed and having a lowermost internal recess 142 within which ispositioned an ejection head 143 formed integrally with an actuatingstern 144. Upon actuation of the ejection head 143 upwardly, the blowmolded article can be stripped from the unitary blow mold 140. Further,if desired, the ejection head is provided with vacuum passage 145extending axially of the stem .144 and communicating with transversecross passages 146 which are vented to the recess 142. By means of thevacuum passages 145, 146 the interior recess 141 of the mold can beevacuated to aid in the subsequent blowing operation, as will behereafter more fully described.

From FIG. 26, it will be seen that the blowmolding operation is carriedout in conjunction with the physical stretching of the blank 130.Further, it will be noted that the blow mold 140 is provided with aninternal ledge or shoulder 147 upon which the upper injection moldsection 114 is seated prior to the blow molding operation. This internalledge 147 projects inwardly, as at 148, to

12 underlie the outermost lower peripheral portion of the chilled edgeof the blank 130. This ledge is provided to cooperate in conjunctionwith the upper mold recess 119 to retain the edge flange 131 of theblank in position during the subsequent processing of the blank.

For example, as illustrated in FIG. 26 of the drawings, the mold element123 is initially actuated downwardly to carry the central portion 133 ofthe blank downwardly inside of the blow mold recess 141 until such timeas the central portion 133 of the blank is snugly confined between theenlarged head 124 and the ejector head 143. Of course, by this action,the medial portions 132 of the blank .130 are substantially stretched.This stretching action is confined to the portion 132 by contact of thehead 124 with the central blank portion 133 and by retention of themarginal blank portion 131 in the manner heretofore described.

Preferably, during this stretching of the blank portion 132, the blowmold recess 141 is evacuated by means of the suction passages 145, 146.Thus, the pressure within the recess 1141 and the pressure exerted uponthe medial portion 130, and the central portion 133 of the blank will beno greater than atmospheric pressure, and the blowing agent in the stillplasticized material can effect blowing of the blank to a cellularstructure.

However, the initial injection molding of the blank 130 has formed anexterior skin on the portions 132 and 133 in the blank in the mannerheretofore described in connection with the embodiment of FIGS. 19through 23, while the peripheral portion 131 of the blank has beenstabilized in a substantially nonexpanded or foamed condition by meansof the circulation of the coolant fluid through the passages 135. Thus,the foaming within the blank portions 132 and .133 will be confinedbetween previously chilled interior and exterior skin surfaces.

Upon final blowing by the introduction of blow air through the centralair vent passage 127 and the transverse air pasage 128 of the element123, a blown article 150, illustrated in FIG. 27 of the drawings, willresult. This article 150 consists of a body portion 151 having anexterior skin surface 152 and an interior skin surface 153 between whichthe walls are foamed to a cellular structure, indicated at 154. Thearticle 150 further has an upper peripheral finish portion, indicatedgenerally at 155, which has been chilled sufliciently during theinjection molding cycle to a substantially noncellular structure.

Of course, the injection molding pressure is released during thetransfer of the injection molded blank 130 from the injection mold ofFIG. 24 to the blow mold of FIG. 25 and this pressure also does notexist during the stretching and blowing operation. As a result, theremay occur certain localized foam areas 156 in the finish portion 155.However, these localized areas 156 are completely surrounded bynoncellular surfaces which are smooth and dense to provide the finishportion essential to a commercially acceptable container.

SUMMARY It will be readily seen that the present invention provides anovel article, such as a container, having exceptionally desirablecharacteristics and possessing exceptional economic advantages. Further,this invention provides a novel method of manufacturing such articles totake advantage of the characteristics of the materials utilized.

The more important and desirable characteristics of the article may besummarized as follows:

(1) The differential density (in the case of a container) of the finishand the body portion is of primary importance. This characteristic makespossible the provision of a container having a dense, hard,surface-smooth finish suitable for the reception of a sealing closureand of a character for adaptation for automatic sealing equipment. Theless dense body portion materially reduces the cost of the over-allbottle without penalizing the desirable characteristic of the finish.

(2) The provision of a laminar body portion wherein the foamed portionsthereof are confined between exterior and interior surfaces which aresmooth, hard, dense for appearance and ink reception at the outersurface and which are hard and dense for product irnpermeability at theinner surface. Of course, by controlled chilling in the injection moldonly the exterior surface or only the interior surface may have suchcharacteristics.

(,3) The confinement of any cellular structure of the finish between thehard, already finished surface layers thereof insures complete fillingof the mold and provides for the transition to the primarily cellularbody portion without an abrupt, radical change in density or othercharacteristics.

(4) The transition zone (which ocurs in the shoulder portion of acontainer) again provides for the change from the dense finish to thefoamed container body and provides an overall integrated structure ofincreased flexing strength, since there is no sharp line of demarcationbetween the container portions of widely varying densities.

Since the density of the body portion is substantially less (preferablyat least one-third less) than the density of the plasticized material,or the material before foaming, important economic advantages can beobtained in' that less material is required to manufacture a containerof a given size or interior volume. Further, the foamed materialconstituting the body is cellular and of a high strength-to-weightratio, particularly when the laminar structure of FIGS. 23 and 27 isutilized.

The method of the present invention is also desirable for severalreasons which may be summarized as follows:

(1) The injection molding of the finish is important to obtain anaccurately dimensioned, stable and substantially noncellular structurewhich is not disturbed or otherwise processed during the foaming of thesubsequently formed body portion. In other words, the finish isinjection molded to its final configuration and changed to a stable,finished state prior to the release of the injection molding pressureand prior to the formation of the container body portion.

(2) The body portion is formed during the formation of the blowablebubble which is subsequently blown to its final configuration. Ofcourse, this foaming step requires the presence of the material in aplasticized state and at a pressure less than the vapor pressuregenerated interiorly of the material by the foaming agent. By properchilling of the previously formed finish and by formation of theblowable bubble a-fter formation of the finish, these conditions can bereadily obtained.

(3) The formation of the blowable bubble can occur in several differentways, i.e., by pinching shut an open ended extruded tube, by pulling orpartially inflating an injection molded shape, or by deflating arelatively flat injection molded shape to a blowable shape. In any eventthe blowable bubble is formed uniformly after the finish has been formedand substantially stabilized without foaming.

(4) Where the subsequently foamed portion of the articles are initiallyformed and partially chilled prior to the subjecting of the material tofoaming conditions, interior and/ or exterior skins can be formedbetween which any subsequent foaming is confined. In a method sense,this is primarily a matter of heat control and the extent, thickness,surface characteristics and other aspects of this skin formation can bereadily varied and controlled.

(5) Of course, the material must remain plasticized, i.e., above itscrystalizing point, throughout the blow molding portions of the cycleand some final foaming may well occur during the blowing and prior tothe chilling of the container surfaces by their contact with the blowmold walls. This affords another process variable by which the extent offoaming may be varied.

(6) The method may be utilized to manufacture articles other than blowmolded containers and the like, e.g., the stopper constructionillustrated in FIG. 18 of the drawings and formed by the process ofFIGS. 16 through 18, inclusive. This method utilizes the the steps ofinjection molding and subsequent forming by foaming but does not utilizeblow molding as a final forming operation. In any event, the article ofFIG. 18 is formed by injection molding at an elevated pressure andfoaming at a substantially reduced pressure following extrusion.

What is claimed is:

1. In a method of making a container having a finish portion and a bodyportion from plasticized thermoplastic material containing an intimatelydispersed foaming agent capable of liberating a gas in said plasticizedmaterial at a predetermined vapor pressure under given temperature andpressure conditions, the steps of (l) injection molding and chillingsaid finish portion of said container to a final configuration in aclosed mold of annular cross-section at a super-atmospheric pressuregreater than the vapor pressure of the gas liberated in said material bysaid agent; (2) injection molding, while chilling to a substantiallylesser extent, additional material from which the container body portionis to be formed; (3) said additional material at the conclusion of step(2) having nonfoamable inner and outer skins and a foamable intermediatelayer; (4) releasing the injection molding pressure; (5) forming saidadditional material into a blowable bubble at substantially atmosphericpressure; (6) enclosing the blowable bubble in a blow mold; (7)injecting air under pressure into said enclosed bubble to inflate thebubble to the final configuration of the body portion of said container;and (8) accommodating foaming of the foamable intermediate layer of saidadditional material between said skins during the performance of thesteps (4) through (7) above set forth.

2. A method as defined in claim 1, wherein step (2) is carried out byinjection molding the second portion to an essentially planarconfiguration, and step (5) is carried out by deflecting the secondportion to a blowable concave-convex configuration.

3. A method as defined in claim 1, wherein step (2) is carried out byinjection molding the second portion between nested, concentric surfacesto an essentially concave-convex configuration and step (5) is carriedout by stripping the second portion from said surfaces.

4. In a method of making an article having a first injection moldedportion and a second blow molded portion, said portions havingsubstantially different densities, and being integrally formed from thesame foamable plastic material containing an intimately dispersedfoaming agent capable of liberating a gas in said material whensubjected to a pressure less than the vapor pressure of the liberatedgas at the ambient temperature; the steps of injecting plasticizedmaterial into a closed mold, a first part of which mold conformsaccurately to the first portion of said article and a second part ofwhich mold preforms between cooperating mold surfaces additionalmaterial from which the second portion of said article shall be blowmolded, said injection occurring at a pressure in excess of said vaporpressure at the injection temperature of said material; chilling saidfirst mold part and said first article portion to an extent such thatsaid first article portion assumes a nonfoamable, dimensionally stablestate; chilling said second mold part and these portions of saidadditional material in direct contact therewith to form nonfoamable skinsurfaces thereon; opening said second mold part prior to completesolidification of said additional material to expose said additionalmaterial, thereby subjecting that portion of said additional materialintermediate said skin surfaces to atmospheric pressure which issubstantially less than said vapor pressure of the liberated gas at theresidual temperature of said additional material, whereupon said foamingagent liberates gas in said portion of said additional material betweensaid skin surfaces to foam said portion; and blowing said additionalmaterial including both said skin sur- 15 16 faces and said foamedportion therebetween to the final 3,389,197 6/1968 Flynn et al. 2645 1Xconfiguration of the second portion of said article. 3,218,375 11/1965Hardwick 2645 1X 3,249,660 5/1966 King 264-51 Ref r n s Cited 3,268,6358/1966 Kraus et a1. 26451X UNITED STATES PATENTS 5 3,137,745 6/1964Johnstone 264 54 PHILIP E. ANDERSON, Primary Examlner 3,144,493 8/1964Santelli 264-51 US 3,145,240 8/1964 Proulx et a1. 26453 264-48, 51, 97

3,225,127 12/1965 Scott 264-54

